Research On Aerodynamic Characteristic Of High Speed Vehicles In Complicated Traffic In Tunnel

Automotive aerodynamic characteristic is the principal and theoretical basis for the automobile body design.It affects vehicle dynamic characteristic,driving stability,security, economy,comfort and environment.It has been an important indicator to evaluate automobile performance.It takes an important role for automobile to win the fierce market competition. With the rapid progress on the development of domesic automotive industry and expressway,it is paid more and more attention on the automotive aerodynamic.As the research on automotive aerodynamic get further, the focus of external flow field research is going to shift from simple modle and steady analysis to real model and unsteady analysis.New reseach field has the characteristics coupling muti-factors. Beacause of the limitation of wind tunnel test,CFD (computational fluid dynamic) is more and more widely applied in new research fields.Subsidized by national innovation project"zhongqi program",aerodynamic characteristic of high speed vehicles in tunnel is on disscution,the result of numerical simulation can provide an instruction for the car design and research.Before the numerical analysis, the hexa mesh of ahmed model, car and tunnel model are created.It takes almost half workload of whole thesis.Then write the program changing mesh.Next,with sliding interface and moving mesh technique provided by STAR-CD software,the transit external flow field around ahmed model is simulated.Compared with the pressure,turbulent kinetic energy,turbulent viscosity,velocity magnitude distribution from steady anlysis,the difference between transit result and steady result is concluded.At last, with sliding interface and moving mesh technique,the 3-D transient external flow field when single vehicle go through tunnel,two vehicles pass each other and one automobile overtake another in tunnel are simulated.The tendency of changing drag and side force is provided.By analyzing the pressure distribution and velocity vector on some sections,pressure pulse on some cells,the reason for the tendency and transient aerodynamic characteristics are concluded.